RELIABILITY AND AVAILABILITY OF CLOUD COMPUTING. Eric Bauer. Randee Adams IEEE IEEE PRESS WILEY A JOHN WILEY & SONS, INC.

Transcription

1 RELIABILITY AND AVAILABILITY OF CLOUD COMPUTING Eric Bauer Randee Adams IEEE IEEE PRESS WILEY A JOHN WILEY & SONS, INC., PUBLICATION

2 CONTENTS Figures Tables Equations Introduction xvii xxi xxiii xxv I BASICS 1 1 CLOUD COMPUTING Essential Cloud Characteristics On-Demand Self-Service Broad Network Access Resource Pooling Rapid Elasticity Measured Service Common Cloud Characteristics But What, Exactly, Is Cloud Computing? What Is a Data Center? How Does Cloud Computing Differ from Traditional Data Centers? Service Models Cloud Deployment Models Roles in Cloud Computing Benefits of Cloud Computing Risks of Cloud Computing 15 vii

3 VIRTUALIZATION 2.1 Background 2.2 What Is Virtualization? Types or'hypervisors Virtualization and Emulation 2.3 Server Virtualization Full Virtualization Paravirtualization OS Virtualization Discussion 2.4 VM Lifecycle VM Snapshot Cloning VMs High Availability Mechanisms 2.5 Reliability and Availability Risks of Virtualization SERVICE RELIABILITY AND SERVICE AVAILABILITY 3.1 Errors and Failures 3.2 Eight-Ingredient Framework 3.3 Service Availability Service Availability Metric MTBF and MTTR Service and Network Element Impact Outages Partial Outages Availability Ratings Outage Attributability Planned or Scheduled Downtime 3.4 Service Reliability Service Reliability Metrics Defective Transactions 3.5 Service Latency 3.6 Redundancy and High Availability Redundancy High Availability 3.7 High Availability and Disaster Recovery 3.8 Streaming Services Control and Data Planes Service Quality Metrics Isochronal Data Latency Expectations Streaming Quality Impairments 3.9 Reliability and Availability Risks of Cloud Computing

4 CONTENTS ix II ANALYSIS 63 4 ANALYZING CLOUD RELIABILITY AND AVAILABILITY Expectations for Service Reliability and Availability Risks of Essential Cloud Characteristics On-Demand Self-Service Broad Network Access Resource Pooling Rapid Elasticity Measured Service Impacts of Common Cloud Characteristics Virtualization Geographic Distribution Resilient Computing Advanced Security Massive Scale Homogeneity Risks of Service Models Traditional Accountability Cloud-Based Application Accountability IT Service Management and Availability Risks ITIL Overview Service Strategy Service Design Service Transition Service Operation Continual Service Improvement IT Service Management Summary Risks of Service Orchestration IT Service Management Risks Outage Risks by Process Area Validating Outage Attributability Failure Detection Considerations Hardware Failures Programming Errors Data Inconsistency and Errors Redundancy Errors System Power Failures Network Errors Application Protocol Errors Risks of Deployment Models Expectations of IaaS Data Centers 87

5 X CONTENTS 5 RELIABILITY ANALYSIS OF VIRTUALIZATION Reliability Analysis Techniques Reliability Block Diagrams Single Point of Failure Analysis Failure Mode Effects Analysis Reliability Analysis of Virtualization Techniques Analysis of Full Virtualization Analysis of OS Virtualization Analysis of Paravirtualization Analysis of VM Coresidency Discussion Software Failure Rate Analysis Virtualization and Software Failure Rate Hypervisor Failure Rate Miscellaneous Software Risks of Virtualization and Cloud Recovery Models Traditional Recovery Options Virtualized Recovery Options Discussion Application Architecture Strategies On-Demand Single-User Model Single-User Daemon Model Multiuser Server Model Consolidated Server Model Availability Modeling of Virtualized Recovery Options Availability of Virtualized Simplex Architecture Availability of Virtualized Redundant Architecture Critical Failure Rate Failure Coverage Failure Detection Latency Switchover Latency Switchover Success Probability Modeling and "Fast Failure" Comparison of Native and Virtualized Deployments HARDWARE RELIABILITY, VIRTUALIZATION, AND SERVICE AVAILABILITY Hardware Downtime Expectations Hardware Failures Hardware Failure Rate 119

6 CONTENTS Xl" 6.4 Hardware Failure Detection Hardware Failure Containment Hardware Failure Mitigation Mitigating Hardware Failures via Virtualization Virtual CPU Virtual Memory Virtual Storage Virtualized Networks Virtual Network Interface Cards Virtual Local Area Networks Virtual IP Addresses Virtual Private Networks MTTR of Virtualized Hardware Discussion CAPACITY AND ELASTICITY System Load Basics Extraordinary Event Considerations Slashdot Effect Overload, Service Reliability, and Service Availability Traditional Capacity Planning Cloud and Capacity Nominal Cloud Capacity Model Elasticity Expectations Managing Online Capacity Capacity Planning Assumptions of Cloud Computing Capacity-Related Service Risks Elasticity and Elasticity Failure Partial Capacity Failure Service Latency Risk Capacity Impairments and Service Reliability Capacity Management Risks Brittle Application Architecture Faulty or Inadequate Monitoring Data Faulty Capacity Decisions Unreliable Capacity Growth Unreliable Capacity Degrowth Inadequate Slew Rate Tardy Capacity Management Decisions Resource Stock Out Not Covered 157

7 XII CONTENTS Cloud Burst Fails Policy Constraints Security and Service Availability Security Risk to Service Availability Denial of Service Attacks Defending against DoS Attacks Quantifying Service Availability Impact of Security Attacks Recommendations Architecting for Elastic Growth and Degrowth SERVICE ORCHESTRATION ANALYSIS Service Orchestration Definition Policy-Based Management The Role of SLRs Service Reliability and Availability Measurements Cloud Management Role of Rapid Elasticity in Cloud Management Role of Cloud Bursting in Cloud Management Service Orchestration's Role in Risk Mitigation Latency Reliability Regulatory Security Summary GEOGRAPHIC DISTRIBUTION, GEOREDUNDANCY, AND DISASTER RECOVERY Geographic Distribution versus Georedundancy Traditional Disaster Recovery Virtualization and Disaster Recovery Cloud Computing and Disaster Recovery Georedundancy Recovery Models Cloud and Traditional Collateral Benefits of Georedundancy Reduced Planned Downtime Mitigate Catastrophic Network Element Failures Mitigate Extended Uncovered and Duplex Failure Outages Discussion 182

8 CONTENTS Xiii III RECOMMENDATIONS APPLICATIONS, SOLUTIONS, AND ACCOUNTABILITY Application Configuration Scenarios Application Deployment Scenario System Downtime Budgets Traditional System Downtime Budget Virtualized Application Downtime Budget IaaS Hardware Downtime Expectations Cloud-Based Application Downtime Budget Summary End-to-End Solutions Considerations What is an End-to-End Solution? Consumer-Specific Architectures Data Center Redundancy Attributability for Service Impairments Solution Service Measurement Service Availability Measurement Points Managing Reliability and Service of Cloud Computing RECOMMENDATIONS FOR ARCHITECTING A RELIABLE SYSTEM Architecting for Virtualization and Cloud Mapping Software into VMs Service Load Distribution Data Management Software Redundancy and High Availability Mechanisms Rapid Elasticity Overload Control Coresidency Multitenancy Isochronal Applications Disaster Recovery IT Service Management Considerations Software Upgrade and Patch Service Transition Activity Effect Analysis Mitigating Service Transition Activity Effects via VM Migration Testing Service Transition Activities 221

9 xiv CONTENTS Minimizing Procedural Errors Service Orchestration Considerations Many Distributed Clouds versus Fewer Huge Clouds Minimizing Hardware-Attributed Downtime Hardware Downtime in Traditional High Availability Configurations Architectural Optimizations Reliability and Availability Criteria Optimizing Accessibility Optimizing High Availability, Retainability, Reliability, and Quality Optimizing Disaster Recovery Operational Considerations Case Study Theoretically Optimal Application Architecture 241 DESIGN FOR RELIABILITY OF VIRTUALIZED APPLICATIONS Design for Reliability Tailoring DfR for Virtualized Applications Hardware Independence Usage Scenario Server Consolidation Usage Scenario Multi tenant Usage Scenario Virtual Appliance Usage Scenario Cloud Deployment Usage Scenario ,3 Reliability Requirements General Availability Requirements Service Reliability and Latency Requirements Overload Requirements Online Capacity Growth and Degrowth (Virtualization) Live Migration Requirements System Transition Activity Requirements Georedundancy and Service Continuity Requirements Qualitative Reliability Analysis SPOF Analysis for Virtualized Applications Failure Mode Effects Analysis for Virtualized Applications Capacity Growth and Degrowth Analysis Quantitative Reliability Budgeting and Modeling Availability (Downtime) Modeling Converging Downtime Budgets and Targets Managing Maintenance Budget Allocation 260

10 CONTENTS XV 12.6 Robustness Testing Baseline Robustness Testing Advanced Topic: Can Visualization Enable Better Robustness Testing? Stability Testing Field Performance Analysis Reliability Roadmap Hardware Reliability DESIGN FOR RELIABILITY OF CLOUD SOLUTIONS Solution Design for Reliability Solution Scope and Expectations Reliability Requirements Solution Availability Requirements Solution Reliability Requirements Disaster Recovery Requirements Elasticity Requirements Specifying Configuration Parameters Solution Modeling and Analysis Reliability Block Diagram of Cloud Data Center Deployment Solution Failure Mode Effects Analysis Solution Service Transition Activity Effects Analysis Cloud Data Center Service Availability (MP 2) Analysis Aggregate Service Availability (MP 3) Modeling Recovery Point Objective Analysis Element Reliability Diligence Solution Testing and Validation Robustness Testing Service Reliability Testing Georedundancy Testing Elasticity and Orchestration Testing Stability Testing In Service Testing Track and Analyze Field Performance Cloud Service Measurements Solution Reliability Roadmapping Other Solution Reliability Diligence Topics Service-Level Agreements Cloud Service Provider Selection Written Reliability Plan 293

11 xv i CONTENTS 14 SUMMARY 14.1 Service Reliability and Service Availability 14.2 Failure Accountability and Cloud Computing 14.3 Factoring Service Downtime 14.4 Service Availability Measurement Points 14.5 Cloud Capacity and Elasticity Considerations 14.6 Maximizing Service Availability Reducing Product Attributable Downtime Reducing Data Center Attributable Downtime Reducing IT Service Management Downtime Reducing Disaster Recovery Downtime Optimal Cloud Service Availability 14.7 Reliability Diligence 14.8 Concluding Remarks Abbreviations References About the Authors Index